The Democratic Party of Hawaii filed a lawsuit in June asserting that allowing every registered voter to participate in the party’s nomination process is tantamount to forced political association and is unconstitutional. The party said it wants to ensure Democrats are selected at the primary stage by those willing to identify as Democrats.

“In short, the DPH’s arguments rest on assumptions about voter behavior that cannot be judged without evidence,” U.S. District Judge J. Michael Seabright wrote in his order finding in favor of the state.

The state defended the open primary, arguing that voting in the Democratic primary is an act of affiliation with the party, preventing voting in other party primaries.

A spokeswoman for the state attorney general’s office said they’re pleased that the judge “fully rejected the Democratic Party of Hawaii’s attempt to limit Hawaii’s primary election to registered members of Hawaii’s political parties.”

“The court upheld Hawaii’s open primary system, which allows voters to participate in the party primary of his or her choice,” Anne Lopez said.

Party attorney Tony Gill said the Democratic Party of Hawaii will “closely evaluate” the decision and may take a few weeks to decide what to do next.

“This issue matters very much to the Democratic Party,” he said. “We think that correct alignment of constitutional rights and the process of primary elections will make our party better, and society better.”

Gov. Neil Abercrombie said in a statement when the lawsuit was filed that he doesn’t support the challenge: “The Democratic Party has always been inclusive, drawing strength from bringing together a diversity of people and perspectives.”

Hawaii has allowed voters to choose which primary they want to vote in since the first open primary was held in 1980.

The party also argued it wants to eliminate the trickery that goes on, when someone votes for a less desirable candidate to improve the chances of a candidate in another party.

Seabright’s order noted that it’s possible, even likely, that some “crossover” voters temporarily affiliate with the party. But he said it’s also likely that given Hawaii’s demographics, a large percentage of primary voters not formally registered with the party “fully considered themselves to be Democrats, and thus were not working to ‘undermine and oppose’” the party.